Many turbine engines employed in aircraft at the present time are cranked for starting through the use of the application of compressed air to an accessory air turbine motor which drives the turbine. The compressed air is variously provided by an auxiliary power unit or from a ground cart or the like.
Unfortunately, the presence of such a starting system requires numerous air ducts, seals and air valves which are not only bulky, and thus difficult to include in a streamlined aircraft configuration to minimize drag, they frequently are heavy as well and thereby reduce the payload carrying capability of the aircraft.
Consequently, consideration has been given to electric starting of turbine engines. As the aircraft typically already include electrical systems and wiring, incorporating an electric starting capability does not appreciable add to the electrical system since it can make use of already existing components and wiring.
Most desirably, a single dynamoelectric machine that is alternatively operable as a generator or as a starter is employed to eliminate the need for separate machines, one for starting and one for power generation. Heretofore, system components employed in operation of the dynamoelectric machine in the starting mode have remained coupled in the system during power generation and vice versa. Particularly during power generation, this results in a decrease in operational efficiency.
The present invention is directed to overcoming the above problems.